The primary objective of this program is to conduct studies necessary to evaluate negative pi mesons (pions) in the management of various solid tumors not well managed by current conventional treatment. This project is being undertaken jointly by the University of New Mexico Cancer Research and Treatment Center (CRTC) and the Los Alamos National Laboratory (LANL). Phase II studies are in progress, with emphasis on treatment of patients with astrocytoma, Grade III or IV, unresectable carcinoma of the pancreas, and squamous carcinoma of the uterine cervix, Stage III and IVA. Phase III trials are active for squamous carcinoma of the oral cavity, nasopharynx, oropharynx, and hypopharynx; inoperable or locally recurrent adenocarcinoma of the rectum; and T3/T4 transitional carcinoma of the bladder. Developmental and clinical physics activity is centered on dosimetry, calculational, and plotting techniques to achieve accurate dose distribution in a treatment volume of arbitrary size and location, with minimum damage to surrounding normal tissues, and development and implementation of technology for pion radiotherapy delivery. Biological studies are being conducted to measure the biological uniformity of pion beams routinely used in patient treatment, and to define biologic actions of pions on both normal and tumor tissues in vitro and in vivo.